The subject matter disclosed herein generally relates to pneumatic turbine starters. More specifically, the subject disclosure relates to cooling of pneumatic turbine starter lubricant.
Aircraft engines, for example, gas turbines, are typically equipped with an air-driven or gas driven turbine starter mounted on the engine accessory gearbox. The functional purpose is to accelerate the engine up to a desired speed prior to ignition of the engine combustor. The turbine starter is typically driven by pressurized air provided by an air source such as an auxiliary power unit, another operating engine, or an external air cart connected to the turbine starter. Pressurized air or gas is fed into the turbine starter drives rotation of starter turbine blades causing rotation of a starter shaft. The starter shaft transmits this rotation to the drive shaft of the accessory gearbox. Rotation of the gearbox shaft drives rotation of a high pressure rotor of the engine which induces airflow into the engine and causes rotation of the engine low pressure rotor assembly. When the engine rotation reaches a desired speed, combustion is initiated.
Typical turbine starters include a lubrication system which delivers lubricant such as oil to the rotating elements of the turbine starter via, for example, a splash system or an oil pump internal to the turbine starter. The service life of the lubricant, and the starter itself, is often limited by the hot/hostile environment of the installation and such installation does not provide cooling of the lubricant that would extend its life, and consequently the life of the starter. Active cooling systems including oil coolers, pumps, filters, etc. are disadvantageous due to weight, packaging size, cost and reliability problems associated with such systems. Other lubrication systems occasionally used in starters mingle lubricant of the engine gearbox with that of the starter to cool the starter lubricant. This approach has disadvantages, however, in that it exposes the gearbox and engine cooling systems to contamination from the starter in the event of starter damage and/or failure. The art would well receive an alternative cooling system for turbine starter lubricant